\times (V - v)^2 = h. p.]

in which A equals the area of blade in square feet, V and v velocities
of current and wheel periphery respectively, in feet per second. Thus,
for example, a wheel 10 feet in diameter with blades 6 feet long and 1
foot in width, running in a stream of 5 feet per second--assuming the
wheel to be giving as much power as will reduce its velocity to one half
that of the stream--the figures will be

6' x 5' 2
------- x 2.5 = 0.468
400

[TEX: \frac{6' \times 5'}{400} \times 2.5^2 = 0.468]

horse power of the wheel.

The total power of the stream due to the area of the blade equals the

Square of the velocity of the stream
------------------------------------ x
Twice gravity (64.33)

volume of water in cubic feet per second x 62.5 (weight of 1 C') = the
value or gross effect in pounds falling 1 foot per second. This sum
divided by 550 = horse power. Thus, as per last example,

2
5
------ x 30 x 62.5
64.33
---------------------- = 1.32 the horse power of the current
550

[TEX: \frac{\frac{5^2}{64.33} \times 30 \times 62.5}{550} = 1.32 \text{
the horse power of the current}]

due to the area of the blades of the water wheel.

For the efficiency of this class of wheel, with slightly curved and thin
blades, divide the horse power of the wheel by the horse power of the
current area, equals the percentage of efficiency.

As in the last case,

0.468 / 1.32 = 0.351/2

per cent. efficiency of the water wheel.

With higher velocities of stream and wheel the efficiency will be from 2
to 3 per cent. less, although the horse power will increase nearly with
the increase in velocity of the current.

For details of application of various forms of current wheels for power
purposes see illustrated description Yagn's and Roman's floating motors
in SCIENTIFIC AMERICAN SUPPLEMENT, No. 463.

A very good example of a floating motor of the propeller class is
Nossian's fluviatile motor, illustrated and described in SCIENTIFIC
AMERICAN SUPPLEMENT, No. 656.

[Illustration: Fig. 24.]

Fig. 24 represents a very complete floating motor, in which the floats
are wedge shaped at the stem, for the purpose of increasing the current
between them, the wheel being an ordinary current wheel, as shown in
Fig. 23, with a curved shield or gate in front, which can be moved
around the periphery of the wheel for the purpose of regulating its
speed or stoppi